Apparatus for finishing patterns and core boxes

ABSTRACT

An apparatus for finishing patterns and core boxes which are used under abrasive conditions and in production operations. The invention concerns the formation of an electroless nickel plating on at least the surface portions of the patterns and core boxes which are subject to wear because of repeated contact with molding and core forming materials. The electroless nickel solution is contained in a holding tank comprising a large inert plastic structure supported by surrounding insulating walls. The plastic tank is removable so that a clean tank can be utilized at all times thereby increasing the efficiency and effectiveness of the nickel plating operation. A circulating system including a heat exchanger and filter means is employed to provide maximum efficiency with respect to the use of the plating solution.

I United States Patent 1 1 3,727,680 Henry, Jr. 1 Apr. 17, 1973 [54] APPARATUS FOR FINISHING 3,365,092 l/l968 Blessing ..220/17 X PATTERNS AND CORE BOXES 3,599,601 8/1967 lshikawa et a1 ..1 18/425 X 3,642,096 2 1972 Val tin ..220 17 X 75 Inventor: Russell Alger Henry, Jr., Albert e Primary Examiner-Morris Kaplan [73] Assignee: Deere & Company, Moline, lll. y- Vincent [22] Filedz Oct. 4, 1971 [57] ABSTRACT [211 Appl' 186333 An apparatus for finishing patterns and core boxes which are used under abrasive conditions and in [52] US. Cl. ..16S/] 19, 1 18/429, 118/603, production operations. The invention concerns the 137/340, 204/242, 220/17 formation of an electroless nickel plating on at least [51] Int. Cl. ..F28f 19/00 the surface portions of the patterns and core boxes [58] Field of Search ..l18/429, 425, 602, which are subject to wear because of repeated contact 1 18/603; 1 17/1 NQ; 137/334, 544, 340; with molding and core forming materials. The electro- 165/ 106, 108, l 19; 204/242, 49, 237, 239; less nickel solution is contained in a holding tank com- 134/ NO; 220/ 17, 63 prising a large inert plastic structure supported by surrounding insulating walls. The plastic tank is remova- [56] References Cited ble so that a clean tank can be utilized at all times thereby increasing the efficiency and effectiveness of UNITED STATES PATENTS the nickel plating operation. A circulating system in- 2,357,536 9/1944 Morse ..118/429 x eluding a heat exchanger and filter means is employed 2,529,699 11/1950 to provide maximum efficiency with respect to the use 2,539,549 l/1954 of the plating solution. 2,897,996 8/1959 3,310,027 3/1967 Lindemann ..1 18/602 X 5 Claim, 3 Drawing Figures PATENTEnAPRmm SHEET 1 or 2 6122 F285 umzE 55. a

M251 M625 nozz. 56w

PATENTED APR 1 7 I973 SHEET 2 [1F 2 FIG. 2

FIG. 3

BACKGROUND OF THE INVENTION This invention relates to the production of patterns and core boxes, particularly patterns and core boxes which are subject to a relatively high degree of wear due to use under abrasive conditions, for example, as is encountered in high pressure molding equipment.

In the production of patterns and core boxes for high pressure molding equipment, the structures are usually formed of cast aluminum or cast iron. Aluminum can be cast economically, it can be cast into intricate shapes, and it requires a minimum of finishing after casting. The aluminum structures are also light and, therefore, easier to handle during molding operations.

Aluminum patterns and core boxes are, however, limited to applications which do not require high volume production of molds and cores. Thus, the aluminum is subject to relatively rapid wear and, in high pressure operations, for example, it has been found that the aluminum is generally not satisfactory where more than about 5,000 molds are to be produced. Attempts to prolong the use of the aluminum will lead to a loss in dimensional accuracy in the molds produced and may also lead to unsatisfactory mold surfaces because of the tendency of the aluminum to become excessively porous after extended use.

Foundries have resorted to the use of cast iron where high volume production of molds and cores is required. The cast iron is harder, and provides a reasonably satisfactory life for the patterns and core boxes used under high pressure conditions. Cast iron patterns and core boxes are, however, more expensive since greater expense is involved in the casting operations and since rather extensive machining is usually required to achieve accuracy and to achieve intricate shapes. The cast iron is also heavier and handling is, therefore, somewhat more difficult.

SUMMARY OF THE INVENTION It is a general object of this invention to provide an improved apparatus useful for the application of electroless nickel to patterns and core boxes whereby an extended life for these articles can be achieved.

It is a more specific object of this invention to provide an improved apparatus for the electroless nickel plating of patterns and core boxes whereby such articles can be utilized under abrasive operating conditions and in production operations without necessitating the use of hard metals such as cast iron for the production of the articles.

It is a still further object of this invention to provide an apparatus for the finishing of patterns and core boxes in the manner described whereby. in addition to providing extended life for the structures, other improvements can be provided including a highly convenient means for determining the degree of wear of the structures, improved release of the structures with respect to molds and cores produced, and substantial savings in production costs.

These and other objects of this invention will appear hereinafter and for purposes of illustration, but not of limitation, specific embodiments of the invention are shown in the accompanying drawings.

2 BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a flow diagram illustrating the treatment steps applied to a pattern in accordance with the teachings of this invention;

FIG. 2 is a schematic illustration of the electroless plating apparatus employed for the finishing of the patterns; and,

FIG. 3 is a crosssectional view of a plating tank devised for use in the plating of patterns and core boxes in accordance with the teachings of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT This invention generally relates to the finishing of patterns and core boxes which are designed for use under abrasive conditions as in high pressure molding machines, or otherwise under conditions which tend to develop wear on the pattern and core box surfaces. The invention specifically involves the formation of an electroless nickel plating on patterns and core box surfaces whereby surprising and highly satisfactory performance of the patterns and core boxes can be achieved.

As set forth in copending Henry et al application Ser. No. 186,129, filed concurrently herewith, and entitled Process for Finishing Patterns and Core Boxes," the techniques go beyond the mere application of a more durable layer on patterns and core boxes. Thus, it has been found that patterns and core boxes are extremely difficult to deal with when it comes to the formation of coatings which will improve the characteristics of these articles. For example, attempts to use a chrome plating or an electrolytic nickel plating have met with only limited success. Because of the rather intricate surface areas of various patterns, the platings could not be applied with any degree of uniformity. It was alsofound that, with the exception of the more expensive chrome plating, the surface hardness of the resulting articles was not sufficiently improved to warrant the expense of such plating operation i The surface characteristics of patterns and core boxes also tend to prevent the successful formation of suitable plating. Thus, most articles of this type are tested prior to plating so that it can be determined if the molds and cores produced therefrom are satisfactory. This testing leads to the contaminationof the pattern and core box surfaces in the sense that sand and other foreign material can become embedded in pores and crevices because of the high pressure of molding. Handling of the core boxes and patterns leads to other contamination such as grease smears.

It would be very uneconomical to attempt plating be fore testing since patterns and core boxes must often be modified to arrive at the dimensions and configurations necessary for production conditions. Therefore, the only economical plating operation which could be resorted to would be an operation which could still function after patterns and coreboxes have been subjected to testing.

The use of an electroless nickel process, particularly for the finishing of patterns and core boxes. The elec troless nickel provides a highly durable, wear resistant and corrosion resistant surface for the articles plated whereby even articles formed entirely of cast aluminum can be used for high volume production of molds with high pressure molding equipment. The electroless nickel can surprisingly be employed in conjunction with patterns and core boxes which are formed of a variety of materials even where such materials are employed together, for example in situations where a plurality of individual aluminum patterns are mounted on a cast iron base. The electroless nickel can be deposited on such combinations of material, and on other combinations including cases where solders of different metallic composition are employed for purposes of reshaping or repairing a pattern surface.

It has been found that the electroless nickel will deposit uniformly even where very intricate surface configurations are involved. Thus, the electroless nickel overcomes drawbacks encountered during experimentation with other plating techniques which generally lead to the non-uniform deposit of material on different pattern areas.

As described in the aforementioned copending applications, the particular techniques employed in depositing electroless nickel on patterns and core boxes initially involve carefully conducted cleaning operations designed to remove all traces of contaminants. It has been discovered that where such contaminants are present during plating, the contaminants will lead to localized areas of inadequate bonding of the plating whereby the plating can be locally removed when subjected to abrasion. Accordingly, without the carefully controlled cleaning operations, satisfactory plating of patterns and core boxes for use under production conditions cannot be accomplished.

The apparatus of this invention which is utilized in conjunction with the aforementioned techniques generally comprises a large holding tank for an electroless nickel solution. The tank is formed of a substantially inert plastic material located on a surrounding supporting structure. The supporting structure includes an inner wall located adjacent the side walls of the tank and a spaced apart outer wall surrounding the inner wall. The space between the walls provides insulation for the tank. A glass fiber re-enforced skin is preferably molded onto a supporting backing for purposes of forming the inner and outer walls.

The tank is combined with a circulating system including a first conduit extending from the bottom of the tank to a pump means. A second conduit connects the pump means to a heat exchanger, and a third conduit connects the heat exchanger to a filter. The solution is continuously circulated by the pump through the heat exchanger and filter with the filter being positioned for discharging the solution into the tank as the solution circulates.

FIG. 1 provides a schematic illustration of the process conducted with the apparatus as well as the steps involved in the cleaning operation. The particular cleaning operations include the initial step of vapor degreasing. This operation will remove relatively loosely held contaminants; however, and particularly because of the aforementioned pattern testing operations, the degreasing will not remove embedded contaminants. The vapor degreasing is, therefore, followed by a cleaning phase comprising either a soak or electrolytic immersion in an alkaline solution.

The cleaning phase may comprise a soak cleaning, particularly where aluminum casting alloys form all or a part of the articles to be plated. The soak is preferably carried out in a non-silicate, non-etch aluminum cleaner. The cleaning compound is used in a concentration of 8 to 12 ounces per gallon of solution maintained between 180 and 200 F. An alkaline 470" solution produced by MacDermid Incorporated provides a suitable composition for this soak cleaning. AI- ternatively, where the articles are totally an iron base material such as cast iron, an electrolytic cleaning bath, or electro-cleaner, can be employed since the iron base material will resist removal of any of the pattern material under the electrolytic conditions.

The soak or electrolytic cleaning is also inadequate for providing complete cleaning since some of the heavily embedded particles of sand and other contaminants will resist removal at this point. Accordingly, the cleaning phase is followed by immersion of the articles in an acid bath. A preferred bath for the acid cleaning where both iron and aluminum alloys form a part of the I article is an inhibited nitric acid solution since this solution will not aggressively attack the iron. Since this invention has particular application to patterns and core boxes formed of a combination of materials such as cast iron and aluminum, the inhibited nitric acid bath provides a particularly advantageous cleaning means. On articles composed of brass, cast iron, and other ferrous metals, a muriatic acid (HCI) pickle is employed as the cleaning phase.

The articles are subjected to rinsing operations after the cleaning and acid bath treatment. In addition, mechanical scrubbing may be resorted to, for example, with brushes. Finally, it may be desirable in some cases to repeat the cleaning and acid immersion steps with or without mechanical scrubbing.

As shown in FIG. 1, the cleaning phase of the operation is followed by a zincate treatment of the articles to be plated where aluminum is present. This pre-treatment of the aluminum surfaces has been found to be ideally suitable for patterns formed all or in part of aluminum. The deposit of nickel from solution can only be satisfactorily accomplished from the standpoint .of uniformity and adherence when the surface to be plated is properly receptive. The zincate treatment has been found to provide a suitably receptive surface for aluminum and does not have any detrimental affect on brass or cast iron, or on any solder materials commonly used in pattern making. The particular zincate solution comprises a combination of caustic soda and zinc oxide and is used at room temperature.

The zincate treatment is followed by a rinse and then immersion of the articles in the electroless plating bath. The patterns and core boxes are preferably provided with a plating having a thickness of about 0.001 inches; however, plating thicknesses between 0.00025 and 0.010 inches are contemplated with the selected thickness depending upon the amount of wear to which a particular article will be subjected. In instances where patterns and core boxes will not be subjected to high volume production or where the surface configurations are such that a great deal of abrasion will not occur, then thicker coatings are not required. In instances of high wear, a thicker deposit may be employed as long as the plating will adhere in a satisfactory fashion without chipping or flaking.

The actual electroless nickel solutions may be of standard composition, for example, a solution initially containing basically 0.7 ounces per gallon nickel and 4 percent sodium hypophosphite. In accordance with standard practice, the concentration of nickel and sodium hypophosphite may be gradually increased as the age of the bath increases. The initial operating temperatures are preferably in the order of 170 to 175 F.

with the temperature increasing up to about 200 F. as

the bath ages.

Electroless nickel plating solutions are relatively expensive, and it is, therefore, important to avoid any-significant waste of such solutions. In typical electroless nickel plating operations, the solutions can be placed in relatively small containers so that only a small amount of solution is being used for plating at any given time. In the event that the solution becomes contaminated, then the relatively small amount can be discarded without any significant loss.

In the system of this invention, many of the patterns being plated are relatively massive and it is, therefore, necessary to use tanks having a relatively large capacity. Five hundred gallon tanks are preferably utilized with tanks in the order of 300 to 700 gallons capacity being generally suitable. It is, of course, much more necessary .to avoid significant contamination when amounts of solution of this magnitude are being employed since it would be a significant loss if it were necessary to discard the contents of an entire tank.

FIGS. 2 and 3 illustrate the particular structural arrangement of this invention. This construction provides an ideal means for conserving the solution and for otherwise providing an efficient arrangement for carrying out the electroless plating. In these figures, a tank 10 contains an electroless nickel plating solution 12. A first conduit 14 extends from the bottom of the tank to a pump 16. A second conduit 18 feeds the solution to a heat exchanger 20. A third conduit 22 passes the solution from the heat exchanger to a filter 24 and the material isreturned to the bath 12 through this filter.

The heat exchanger 20 includes a steam inlet pipe 26 which serves to pass the steam through an annular jacket surrounding the heat exchange conduit which contains the solution. The steam is passed out through a conduit 28 for recycling.

Additives are introduced to the solution either continuously or at desired intervals. These materials may comprise amounts of nickel and sodium hypophosphite for increasing the ratios of these materials in the solution and for replenishing amounts which have been deposited during plating.

FIG. 3 illustrates a preferred structural form for the tank 10. This tank includes a plastic liner 32 formed of a material which will be inert as far as the electroless plating operation is concerned. Polypropylene is a particularly suitable material for this purpose. The liner 32 includes an outwardly extending outer flange 34 which rests on the top wall 36 of a supporting structure for the liner. The wall 36 includes a downwardly sloping outer edge portion so that the exposed surface of the tank assumes a like configuration. If any of the solution in the tank should be splashed into this area, the solution will flow away from the tank thereby reducing the possibility of contamination.

The tank supporting structure includes a glass fiber skin portion 38 and inner and outer plywood portions 40. The plywood panels 40 are separated by means of 2 X 4s 42 thereby providing a spaced apart relationship for the panels 40 so that the construction is inherently characterized by an insulating space 44 with the glass fiber adding to the insulating ability.

In a typical embodiment, the liner 32 comprises an integrally formed tub having 8 1 inch thick side and bot tom walls. The plywood panels are be inch thick and an approximately 1% inch thick glass fiber re-enforced skin is molded around the plywood.

Since the electroless plating solution is kept at an elevated temperature to provide for the most efficient deposit of plating material, the insulated structure of FIG. 3 is particularly advantageous. In addition to the inherent insulating character, the arrangement described is structurally strong so that the weight of the solution can be readily handled.

By forming the liner of polypropylene and by completely cleaning the liner before the introduction of solution, contamination of the electroless bath can be held to a minimum. The use of a liner formed from an inert plastic and of a very clean character is important since the electroless nickel has a great tendency to form deposits on surfaces of many different types. In addition, the electroless nickel will begin to deposit on any portions of a surface which have even a small amount of contamination or which are scratched since these conditionsprovide a nucleus for the buildup of nickel.

Particularly due to the flange 34 formed on the liner 32, the liner can be very easily handled by simply locating the liner within the supporting structure in the manner illustrated. The additional advantage of a removable liner 32 is thus achieved. Thus, the liner can be easily lifted up and replaced if it becomes damaged or otherwise unsuitable for use. The liner material is very suitable for cleaning, and the liner as well as the other portion of the system can be efficiently cleaned by circulating nitric acid through the entire system at periodic intervals. I

The advantage of the illustrated structure will be readily apparent since any danger of contaminationis greatly minimized. Accordingly, an electroless nickel bath can be used throughout its entire useful life with the need to discard a full bath being virtually eliminated. As indicated, the electroless nickel baths are extremely expensive, and therefore, a system which avoids the loss of such a bath is of great value.

The other components of the illustrated structure are also formed of materials which are inert so that the buildup of nickel deposits in the circulating system can be minimized. Chlorinated polyvinyl chloride piping is preferably employed for the conduits l8 and 22. The heat exchanger may comprise Pyrex internal conduits for carrying the solution and outer steel pipe for containing the steam in the annular space between these pipes and the internal conduits of the heat exchanger. The filter 24 preferably comprises a polypropylene bag adapted to filter out particles of a size greater than five microns. The use of this filter is quite important from the standpoint of avoiding the introduction of solid particles into the plating bath which could serve as nucleating points for the unwanted deposit of nickel.

In addition to plating of previously unplated articles, the system described is useful for the replating of articles which have been used to the point that excessive wear has occurred in one or more locations, or where some mistake was made in a previous plating operation. The replating process is preceded by a stripping operation for purposes of removing any portions of the previously applied nickel plating. The stripping operation is desired so that the nickel will deposit uniformly over the entire surface without any areas having an excessivelythick buildup of nickel.

The system has been described with reference to the application of platings to aluminum and cast iron patterns and core boxes. it is contemplated, however, that other pattern materials, for example, epoxy or epoxy impregnated with metal can be advantageously employed in the operation of this invention.

In view of the cost of the electroless nickel solutions, it is desirable to avoid plating on areas which will be out of contact with the molding and core forming materials. Accordingly, the pattern and core box areas are masked, and it is again necessary to use materials which will not lead to contamination of the plating bath. Plastisol tapes and plastisol based paints, and polyethylene bags or sheets are examples of materials which can be used to protect areas which are to be held out of contact with the nickel plating solution.

When electroless nickel plating is provided on patterns in the manner described, various other advantages have been recognized in addition to the improved pattern life. Specifically, the separation of the pattern surfaces from the molding material can be accomplished much more easily, this apparently being due to the extremely smooth surface provided by the deposited-nickel, and also by the lubricity provided by the phosphorous content of the deposited material. The wear of plated articles can also be readily detected due to the fact that the deposited nickel has a silvery-satin appearance providing a contrast with the materials employed for pattern and core box making. Accordingly, when an area of nickel plating has worn away, this fact will be readily observable because of the contrast between the exposed article surface and the remaining nickel plating.

The improved wear is due to the hardness of the electroless nickel when compared with the aluminum and cast iron. Cast aluminum typically has a Brinell hardness number of about 80, cast iron about 200 and electroless nickel about 500. The electroless nickel hardness can be further increased by heat treatment; however, this has not been necessary to obtain the improvements discussed.

in addition to the aforementioned advantages of the electroless nickel, the use of the system provides significant savings in a foundry operation. Thus, for articles to be used for high volume production, it is approximately 40 percent cheaper to nickel-plate than to produce a pattern or a core box from cast iron. Even where the more expensive cast iron articles are employed, the electroless nickel plating still provides improved wear characteristics, improved separation, and the visual wear indication.

It will be understood that various changes and modifications may be made in the above-described invention which provide the characteristics of this inventron without departing from the spirit thereof particuwalls of said tank, and a spaced apart outer wall sur-.

rounding said inner wall, said inner and outer walls each comprising a plastic coating bonded onto a supporting backing the space between said walls providing insulation for said tank, and wherein 'said tank is removably received within said supporting structure.

2. A construction in' accordance with claim I including circulating means for handling the electroless nickel solution to be used in said tank, said circulating means including a first conduit extending from the bottom of said tank to a pump means, a second conduit extending from said pump means to a heat exchanger, and a third conduit extendingfrom said heat exchanger to a filter, said solution being continuously circulated by said pump from said tank through said first and second conduits, through said heat exchanger, and through said third conduit to said filter, said filter being positioned for discharging said solution into said tank.

3. A construction in accordance with claim 1 wherein said coating is a glass fiber re-inforced plastic.

4. A construction in accordance with claim 1 wherein said supporting structure defines an upper wall extending between said inner and outer walls, said tank defining an outwardly extending flange adapted for positioning on said upper wall for thereby locating said tank relative to said supporting structure.

5. A construction in accordance with claim 1 wherein said supporting structure includes downwardly sloping shoulder portions whereby any solution spilling onto said shoulder portions will be directed away from said tank to thereby avoid contamination of solution in the tank. 

1. A construction for applying an electroless nickel plating on surfaces of articles comprising patterns and core boxes designed for use under high pressure conditions in molding and core forming equipment, said construction comprising a large electroless nickel solution holding tank formed of polypropylene, a supporting structure surrounding said tank, said supporting structure comprising an inner wall located adjacent the side walls of said tank, and a spaced apart outer wall surrounding said inner wall, said inner and outer walls each comprising a plastic coating bonded onto a supporting backing the space between said walls providing insulation for said tank, and wherein said tank is removably received within said supporting structure.
 2. A construction in accordance with claim 1 including circulating means for handling the electroless nickel solution to be used in said tank, said circulating means including a first conduit extending from the bottom of said tank to a pump means, a second conduit extending from said pump means to a heat exchanger, and a third conduit extending from said heat exchanger to a filter, said solution being continuously circulated by said pump from said tank through said first and second conduits, through said heat exchanger, and through said third conduit to said filter, said filter being positioned for discharging said solution into said tank.
 3. A construction in accordance with claim 1 wherein said coating is a glass fiber re-inforced plastic.
 4. A construction in accordance with claim 1 wherein said supporting structure defines an upper wall extending between said inner and outer walls, said tank defining an outwardly extending flange adapted for positioning on said upper wall for thereby locating said tank relative to said supporting structure.
 5. A construction in accordance with claim 1 wherein said supporting structure includes downwardly sloping shoulder portions whereby any solution spilling onto said shoulder portions will be directed away from said tank to thereby avoid contamination of solution in the tank. 